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[FreeRTOS Home] [Live FreeRTOS Forum] [FAQ] [Archive Top] [March 2006 Threads] Nested semaphore lockingPosted by Nobody/Anonymous on March 6, 2006 Hello,
is there any simple way to extend FreeRTOS semaphores to add nesting? Like in:
xSemaphoreTake(s, portMAX_DELAY); /* obtains s */ xSemaphoreTake(s, portMAX_DELAY); /* does not deadlock! */ xSemaphoreGive(s); /* does not free s */ xSemaphoreGive(s); /* really frees s */
I tried to implement it on top of FreeRTOS semaphores, but it's quite tricky.
RE: Nested semaphore lockingPosted by Nobody/Anonymous on March 6, 2006 I've solved the problem like this. Does it look sane?
typedef struct Semaphore { xSemaphoreHandle lock; xTaskHandle owner; int nest_count; } Semaphore;
void sem_obtain(struct Semaphore *s) { if (s->owner != xTaskGetCurrentTaskHandle()) xSemaphoreTake(s->lock, portMAX_DELAY);
s->owner = xTaskGetCurrentTaskHandle(); s->nest_count++; }
void sem_release(struct Semaphore *s) { ASSERT(s->owner == xTaskGetCurrentTaskHandle());
if (--s->nest_count == 0) { /* Disown semaphore */ s->owner = NULL; xSemaphoreGive(s->lock); } }
RE: Nested semaphore lockingPosted by Nobody/Anonymous on March 6, 2006 Probably very sane, as I don't really under stand it :-)
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